BIO - Membrane transport and enzymes

Please explain the following -

1. If only potassium leakage determined membrane potential, what value would membrane potential have in millivolts?
2. What kind of plasma membrane molecule does phospholipase C act upon? ( I understastand it cleaves the glycerophosphate bond) 
3. What enzyme is needed to catalyze conversion of arachidonic acid into prostaglandin signal molecule?? 
4. The proteins that lipid-soluble signals like thyroid hormones must bind to for travel in the blood are called ??? ( I understand that transport proteins that are water soluble transport them in the blood)